In article <pev3ra$eqq$
1@Iltempo.Update.UU.SE>,
bqt@softjar.se says...
On 2018-06-02 18:58, Nootrac90 wrote:
On Thursday, May 31, 2018 at 11:22:22 AM UTC-4, Johnny Billquist wrote:
On 31.05.18 01:44, Nootrac90 wrote:
I'm working on a Basic-Plus program under RSTS/E v07 that uses random access files. One of the files uses a record size of 32 and yet a ten record file takes up 10 blocks.
Am I wrong in thinking that these 10 records (and a few more) should fit into one block?
10 EXTEND
1000 OPEN "TSTFIL.DTA" AS FILE 2%, RECORDSIZE 32%
1010 FIELD #2%, 32% AS RD$
1020 LSET RD$ = "[123456789012345678901234567890]"
1030 FOR RN% = 1% TO 10%
1040 PUT #2%, RECORD RN%
1050 NEXT RN%
1060 CLOSE #2%
32767 END
It has been nearly 40 years since I worked with these files and I feel like I've forgotten something. Any help would be greatly appreaciated.
Not sure if this is any help. I don't have RSTS/E, and don't have
BASIC+. However, I did try this on RSX with BASIC+2, and for that, the
one thing missing was the adding of "ORGANIZATION RELATIVE" to the open
statement. After that, it worked fine, and produced a file as you would
have expected.
But I can't remember if you needed that, or if it is even a valid
keyword to OPEN in BASIC+...
I have not seen the ORGANIZATION RELATIVE keywords in any of the Basic-Plus manuals or books I have seen. That being said, I still tried it.
I added ", ORGANIZATION RELATIVE" to the end of line 1000 and got "?Modifier error at line 1000"
Ok, so not valid in BASIC+ then. Oh well. I guess someone should take a
look in the BASIC+ manual on PUT as well as OPEN, and see if there are
any hints on this in there.
Sorry that I couldn't help.
Johnny
ORGANIZATION RELATIVE (and such like) require RMS and are
supported only in BASIC-PLUS-2 (BP2), not in BASIC-Plus
(B+).
I don't know if the B+ documentation is online anywhere.
Look for RSTS/E documentation. I have a set but you can't
have it :-) BP2 (and VMS BASIC) are mostly supersets of
B+, but that doesn't help much when you are trying to
avoid BP2 and VMS BASIC extensions.
The RECORD clause on the B+ put statement is the (512-
byte) block number, nothing to do with the RECORDSIZE
clause. RECORDSIZE (IIRC, it's been years) determines the
buffersize for a file opened using record i/o (as you are
doing.) It is rounded up to the next multiple of 512,
which is the RSTS/E (and many other systems of that
vintage) disk block size. (I think on tapes, the
RECORDSIZE must be a multiple of 2 and on terminals, it
can have any value (greater than 72, the width of a
teletype?). On lineprinters, it is always the lineprinter
width, usually 132, and other values for other devices.
(The concept of device-independent I/O was pretty new and
not always honored...)
To make records of arbitrary sizes, you need to read and
write blocks and extract (or map) your data records using
the FIELD statement. You need to RSET strings to fields
or copy the fields to working strings, and you need to use
various CVT functions and CHR$ to convert non-string data
(integers, floating points, bytes, etc.) to and from
strings. You need to decide, if your records are not
divisible into 512, whether you want them to span disk
blocks and handle that yourself.
What might work better for this application is using a
virtual string array. Open the file and then say "DIM #
<channel number>, <string variable name>(<number>)=
<length>" (Check the syntax, no guarantees) For your
example, something like "DIM #2%, RD$(10%)=32%" This will
make an array of 32-byte strings, addressable as RD$(0%)
through RD$(20%). B+ will handle reading and writing the
disk file, unblocking the records, etc. You will still
need to convert the RD$() elements to what ever form you
need, using mid(), cvt$%(), cvt$f(), etc. to extract data
elements, and string concatenation, cvt%$(), etc. to
construct RD$() elements.
Virtual arrays can be two-dimensional, and they can be
arrays of integers, floats, or fixed-length strings. I
think you can create more than one array in a given file,
but you need to be careful all programs that use that file
define it exactly the same way, or chaos ensues. Also,
the maximum size of a virtual array is only either 32767
or 65535 (15 or 16 bits, forget which)
To write record 19 in the virtual array, just:
RD$(19%) = <some string variable or expression>
and it will write it to disk when you either close the
file or reference an array element in a different disk
block.
To read record 7, just (after opening the file)
s$ = rd$(7%)
Virtual arrays are supported in BP2 and VMS BASIC, but due
to the limitations and the far greater flexibility of RMS
and record types in both languages, are very rarely used.
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